Problem with engine hesitation, might be simple.

I have a 2006 Chevy Cobalt LS (4 door-sedan) with 52,800 miles. Sometimes when I slow down and stop at a street light (not a speeder and don't stop fast), it seems like my car wants to stall. When I get moving again it's fine, it could be a simple thing to fix but any suggestions?

I change the oil, oil filter, air filter, carbon air filter every 3,000-3,500 miles but, still seems like something else is clogg. None of the sensors comes on. Don't want to take my car to a chevy dealer to get service if I don't have to. Trying to save money. Anything is helpful.

Comments

When was the last time you got a good tune-up done on your Cobalt? Clean the injectors, change the spark plugs (even if G.M. says only at 100,000 miles), check or change the wires (might be damage)? It's nice to change all the filters but there's a little more to it.

Ever since I brought my car (March 2006) I never had a complete tune up on it, besides the basics. Change the spark plugs about 3 weeks ago, at first, it didn't want to start. After a few tries, my car finally did start. The wires are in good condition, also the hoses, clamps, gas cap, and couple of bolts needed tighten. Never clean the injectors, though. Or the fuilds.

Going on a vacation on April 29, 2009 to Pennsylvania, It's going to take 8 hours of driving or 450 miles. Do you think it is the injectors that could be causing it? How can I clean them?

Pep Boy or Auto Zone must sell what you need for that. I've seen people do it by themselves. You plug this injector cleaner (it looks like its a bottle) somewhere on the engine and start the car and it seems to do the job by itself as the engine runs. I usually go to the dealer but you seem to like to do your own work on your car.

Did try the injector cleaner, it seems like it's working. I'll give it 2 days to see results. The engine runs alot quiet now. Hopefully it works, thanks. By the way, sometimes the "check gas cap" sensor comes on once in awhile. Do you think the hesitation has anything to do with that also?

It's possible and probably it is. With today's electronics and computerized gadgets in cars anything is possible. I had a car once and at every fill-up I had to turn the gas cap at least 3 full turns (clicking sound) if not my "check engine" light came on. The first time that this happened to me it cost me 10$ at the dealer to know this and to reset the system. The mechanic said I could do it by myself by turning my key to acc. 40 times "non stop". Go figure!

Now I'm thinking of it, can't be the gas cap because did brought a new gas cap about 3 months ago locking method with key lock. On cap, it says 3 full clicks to lock. (probably with the same one you have also) About a month ago, when left the driveway, the gas cap sensor came on. But, the hesitation started in june 2008, the car dealer service department couldn't fine anything wrong. Yet It still pass inspections and pre-trip inspections from this day. (I drive 18wheelers)

Anyways, the injection cleaner (so far) is working. At street lights fully stopped, the engine runs alot quiet than what it was running before couple of days ago. Not sure if it did the trick or not, but it's helping. I'm going on a vacation on wednesday leaving VB,VA to Pittsburgh, PA (450 miles/8 hrs) it will be a long trip. Of course, driving, rather drive anyways. Getting an oil change before going up and hopefully it does fix the hesitation this time, could use your advice more. Can you think of anything else that could be causing it?

Good point, I run Shell V-Power 93 or Kwik Trip 91 for you Midwesterners with no ethanol and I will consistently get about 2 MPG better than ethanol lased regular. I am currently running 150 miles a day. Doing my motor good.

Just got back from vacation 2 days from Pittsburgh, PA, the engine hesitation have gone away, but now something else occured when I came back. I think something is wrong with the transmission. Anyways, no matter what speed I go, when I need to slow down to make a stop, of course the rpms will go down. But around 10-5mphthe rpms goes up another 100 and then goes down to normal. Then the light bulbs dimmers for a few seconds. There is no leaks, and in the vehicle menual, it says to change transmission fluid and filter every 50,000 miles. My car now has 54,944, probably it is time.

Before I do get it change, any ideas on what else could be causing it for I can find alternatives without having to spend alot of money. Any feedbacks is helpful? sorry about asking to much questions?

Thanks for all your help, and sure enough more problems will occur soon or later. However, I do have just one question? Could be a dumb question, but need to know. Actually two questions, 1. How can I check the transmission fluid? ever since I bought my car, could never find the dipstick for transmission fluid. and 2. Does cobalts have a fuel filter? if so, can you please tell me where it is located for I can change it.

1. Transmission doesn't have a dipstick. There is a plug on top of the transmission. You would be better off letting a dealership check it.

2. The fuel filter is under the car between the fuel tank and back seat. If you look under the car between the two rear wheels, there is a metal beam connecting the rear suspension. The fuel filter is above the beam.

When I were finish washing my car on Monday, and were using a towel to dry off my car, I've notice the driver's side headlight had mositure inside the len cover. Never had that problem when washing any of my vehicles before. Anyways, I checked for cracks on the len, gaps around the len and couldn't find anything that could cause it.

The headlight and turn signal bulb still works fine. Should I be concern about it? What do you think? Just for the record, my car were sitting for about an hour or two after I drove it to somewhere, and it was 75 degrees outside that day. Also, the passenger side don't have that problem, yet. Any advice?

I did found the solution about the moist in the headlight lamp. Which still occurs now and then but, there is a another minor problem which could lead to major. Here it goes, everytime when I need the defoggers while driving, my car starts hesitating when slowing down at a traffic light on red.

Well, in other words, when slowing down to 5 mph my rpms starts frustrating between 700 up to 1300 rpms at 3 mph. When my defoggers (defrosters) are on but, when I turn off the defoggers (defrosters) it returns to normal readings. I know it probably doesn't make any sense to you either but, any advices will be hopeful.

Next 2-3 weeks I will buy a book for repairs, do you think Advance Auto Parts or Auto Zone will have one?

I assume by defoggers you mean your defroster mode of the HVAC controls. When you select the "DEfrost" setting, your AC compressor automatically kicks in. When that happens, the PCM tells the engine to increase the idle speed because of the increased load of the compressor. Your engine cannot hold that new idle speed and the speed starts fluctuating. The problem could be: rapid cycling of the AC compressor caused by insufficient R134a charge or a dirty throttle body causing the bypass air around the throttle plate to give an erroneous reading to the PCM. Start by looking at the throttle plate and throttle body and clean if necessary. Does your AC work OK? If not, look at getting the system diagnosed and recharged.

I had the AC fixed 2 years ago or alittle lesser. I only used the AC twice this year and the first time this year, my car ran normal with it on without the fluctuating. Actually, the first time was when I where driving on the interstate but, for the second time I used the AC, that's when the fluctuating started. (About 4 months ago.)

Do you think I should buy a new PCM? About the throttle plate and body, I know this is a stupid question to ask but, Can you tell me where the throttle plate and throttle body is located? Wished I were a mechanic. However, I do fix some minor repairs. Definitely, next paycheck I will buy a auto repair book.

Also, one more thing. What's the best place to go to buy a auto repair book?Sorry about asking too much questions.

No, don't buy a new PCM. The throttle body and plate are located at the intake manifold. Follow the big black plastic tube from the air filter box to the engine. You need to remove this tube to get at the plate. Do yourself a favor and buy a Haynes manual at any auto parts store. You need to know what you're doing or you can seriously damage your engine if you drop something into the throttle body. I would suggest seeking the help of someone who does know what they're doing so you can learn by watching. Otherwise, take the car to any reliable shop. These cars and engines are everywhere and are easy to work on and diagnose.

I will take my car in to the shop next Friday, also for an oil change. I was going to attempt taking off the air filter and housing to check the throttle body but, like you said "need to know what you're doing or you can seriously damage your engine if you drop something into the throttle body" I didn't want to risk it.

Overall, everything else runs good, some minor repairs but nothing major yet. Although, my 06 Cobalt LS has about 59,801 miles. Had 105 miles since I got my car almost brand new. In Sept. 2006 I fell asleep at the wheel and done about $4,000 in damage to the front end of the car. still concerns me, what else could go wrong.

Are you a mechanic? if so, maybe you can teach me a thing or two. Thanks again for your help and hopefully the shop can fix the problem without it being too expensive.

No, just an experienced (40+ years) DIY'er. I learned on points and condenser ignitions, carburetors, and no computers. Very different today. Easier in some respects but much more difficult to diagnose when problems do arise. Unless you have a factory scan tool it's best to bite the bullet and take it to a competent mechanic. You'll pay less in the long run than just throwing replacement parts at the engine until you find the problem.

Well, I took my car to the shop but, they said they couldn't find anything wrong. Nothing wrong with the senors, even the check engine light doesn't come on. Once in awhile it does when the gas cap is loose. The throttle body is clean, filters are good, guess I shouldn't worry about then. Until, it does gets alot worst. Still doesn't seem right. Any suggestions about the last recently message I've posted or Ideas? Thanks.

Tomorrow morning (08/21/2009) I will bring my car in the shop for an Oil Change.Also, getting new filters, and was thinking of getting the O-Ring (something like that) replaced as well. Never change the O-Ring while getting an Oil Change for any of my vehicles I used to have. Anyways, Should I get the O-Ring or some kind of ring that is use for the Oil, replaced?

I heard someone saying something about an O-Ring was bad and Oil kept on leaking, as she took her car in the shop for an Oil Change and asked about the leaking problem. The mechanic said a Ring was bad which caused the oil to leak and she suggest everyone to get the Ring replace while getting the oil change.

Not sure what O-Ring (something use to protect leaks, besides the seal or gasket) she was talking about. Maybe, someone might know. Can someone help me understand, wished I were a mechanic, as I still haven't brought a repair book yet.

By the way, I will be going to Tontitown, Arkansas hopefully before the weekend, so I'll keep everyone posted. Thanks...

The only O-ring I'm familiar with in the oil change procedure is a large O-ring located in the oil filter cap. I have never had to replace this O-ring in over 5 years of changing the oil and filter on a 2.2L Ecotec engine. If the O-ring was leaking, there would be an oil leak all over the oil filter housing located at the right-front of the engine. That being said, some oil filters (NAPA in particular) come with a replacement O-ring. I know for a fact that AC/Delco (factory GM part) does not. The O-ring is cheap. Don't let them sell you a new oil filter cap and O-ring together. They may try that. You can purchase the O-ring separately. If it's not leaking, don't even worry about it.

Everyone has been a great help. I'm intending on moving back home to Pittsburgh, Pennsylvania on the 8th of October 2009. Not sure when I'll be posting again on these forums. Couple more days left, can't wait to leave Virginia Beach. Sucks down here.

Anyways, recently...my car mpg is dropping fast and now, close to 29.1 and it was 32.7. Notice it dropped last Wednesday. Not sure why, could be alot of different reasons. Last week, one of the tires were at 10psi (got it repaired.) All the tires are set at 32psi for now. Until, I leave, then I'll set them at 30psi (since it will take 7.5 hours of driving.) Had an Oil Change and Air Filter new, about a month ago. Do want to get a new fuel filter, but I have to wait til March 2010. So, Any advices that can help my car get more mpg? By the way, I haven't been using the Interstate in awhile. I know for a fact, that I can get my car up to 34mpg all the time, by moving back in the country. Where the country roads exisits. But, what else can help the mpg? Anything is helpful. Again, thanks....

The drop in mileage is not necessarily meaningful to me. If no engine lights are on and th engine runs well there probably isn't anything actually wrong.

First you had a very low tire, so low it may have damaged the sidewall. The tire store would have warned you if they thought it had happened. That tire hurt the mileage reading you had been getting.

Second we have switched to winter gasoline. It is a higher volatility cut of the distillate. That gives better starting for cold engines when incoming air is colder than summertime, but it hurts fuel mileage. Also you may have been getting gas that has more alcohol in it. The alcohol hurts your fuel mileage. Try using only name brand gas when you can and you'll probably see a difference.

Third, I have the tires in my Cobalt at 36 instead of the recommended 30. That helps mileage. It hurts the ride some. But especially on a longer highway trip the gas mileage increase will be meaningful.

Fourth, I don't think GM recommends changing gas line filter unless there's a problem with fuel pressure. If you have 120,000 miles and occasionally buy gas from the cheapie stations that aren't brand stations, you might change it just in case you got some gunk somewhere. But most stations have filters inline or actually on the hose that filter out "stuff." Save the money for the fuel filter for something else.

Fifth, the only thing I'd chance wasting a little money on would be a 12 ounce size bottle of Techron fuel system additive, not the injector cleaner which is cheaper. It's at Walmart or Advance Auto or others at about $5.95. I think one newspaper ad this week had two for $7.95, the alleged regular price. I'd put that in like that bottle says when the tank is fairly low, while you're ready to pump gas in, then fill the tank. It _might_ clean your injectors and fuel system. The gasolines usually keep injectors clean. Another option is to fill up with something like Shell's Premium V fuel WHEN your tank is about half full already so you're mixing regular and premium and ending up with about Plus grade octance; you don't need highest octane, but the cleaners might help instead of using Techron additive. There are supposed to be extra additives in the higher grades of fuel; it might, might clean up injectors if there is anything crud on them. Other people probably have their preference of additives but mine has been Techron through the years. I only use it maybe twice a year because I pick up a bottle when I see it on sale at one of the auto parts box stores.

First one: The tire repair shop, had to take out a nail out of one of the treads, didn't go thru the sidewall. Luckly, it didn't puntion the tire. So far the psi is holding 32.

Third one: Will it be better to set all the tires at 36psi? On Thursday, of next week, I'll be hauling up to 400 lbs on a 443.5 miles drive. Will it still be safe enough? According to your cobalt, at 36 psi, what is your Cobalt mpg aveage?

and Fifth one: According to the driver's manual, my Cobalt should only use 87 brands, Will it hurt the engine if I use 89 brands (or Premium)? And one more question, sorry about asking too much questions, btw. Does Techron fuel system additive works? Since you been using it for years, Does it cleans the whole fuel system and what else does it do?

The tire pressure varies 1 pound/sq in with every 10 degrees up or down Fahrenheit. At typical outside temps now of 60 degrees in mornings my gauge shows 35 or 36. It used to be 37-38 when mornings were warmer. I find the dash gauge shows one tire higher. Don't trust the tire sensors; get your own $1 gauge and set the tires yourself when cold. 36 should be good; pressure will increase some with tires warming up and especially with a load.

The Techron was an early additive package by Chevron sold at stations. BMW long ago when gasolines weren't carrying good enough additives in some cases recommended Techron. It was the same additives used by Chevron in their gasolines. Since then government intervention required better additives in all gasolines, including regular. I still use Techron rather than other over-the-counter brands just because I feel it works. A Cincinnati car repair talk show guy recommended it for cleaning injectors up until he went off the air a year ago. He owns a body shop and major independent repair place in a high end part of the city. He was a graduate of the local vocation school for the county. He knows his stuff.

It also cleans and protects the fuel gauge sensor potentiometer metals against deteriorating from sulfur in gasoline. GM had a few gauges that would corrode from that and give erratic readings. In the past decade when I would put it in and drive the car, the car seemed to run better after half an hour's driving. I believed it did clean up what some gasolines left on injectors. Then I used to buy cheapest gas and mix brands about half and half with known name brands. Now I buy Kroger's gas, Mobile/Exxon, and Shell. Rarely anything else. I don't notice as much effect after putting it in the last couple of years. I consider it throwaway money spent for the additive. If I didn't use it I would probably occasionally spend extra money and run a couple of fillups of premium Shell/Texaco, Mobile, or Marathon thinking I was cleaning up the fuel system with the supposed better additive package in the premium. (We don't have Chevron in this area anymore.) Since the car doesn't need premium, I would only do that for a couple of fills--the first fill had 87 octane gas mixed with premium while the second would increase octane above 89 for the mixture.

A little philosophy here: most stations mix premium and regular to get the Plus grade. So I'd rather just add some gallons of premium where I know I'm getting 100% additives and gas rather than trust their computerized mixing ratio and just buy Plus.

The Techron Fuel System Cleaner supposedly does more for the whole system; an identical looking bottle is called Techron Injector Cleaner and I believe it contains less additives overall because it's usually cheaper.

My personalized advice would be add a 12 oz bottle of TEchron to a low tank, fill with premium. Drive it down to half a tank and refill with quality brand premium. Then use regular of a good brand. Do that for your trip. Occasionally put in a few gallons of premium to fill your tank. Otherwise use quality brand regular to avoid alcohol in higher percentages which cuts gas mileage.

i have an 06 chevy cobalt ls and i have the same problems as you when i stop at a light, or turn the air or the defrost on the car wants to idle bad just wondering if you have found the problem if so i really need to know ive changed the map sensor and a few other thing still hasn't solved my problems the car is getting to the point were it will stall itself out thanks...